This invention relates to a clean transfer method and an apparatus therefor, and more particularly to a clean transfer method for transferring an object to be transferred (hereinafter referred to as "transferred object") required for processing and/or assembling a product associated with a semiconductor, an optical disc or the like while keeping an operating environment clean and free of any contamination, and an apparatus therefor.
The assignee proposed a method for transferring a transferred object between various processing units such as a film forming unit and the like by means of a clean transfer carrier which is provided therein with a vacuum clean chamber and a transfer means for transferring the transferred object in the vacuum clean chamber, as disclosed in co-pending U.S. patent application Ser. No. 902,720 now U.S. Pat. No. 5,364,219 filed by the assignee based on Japanese Patent Application No. 177803/1992, of which the disclosure is incorporated herein by reference.
Unfortunately, it was found that the transferring method proposed by the assignee which utilizes the cleans transfer carrier provided with the vacuum cleans chamber for receiving the transferred object therein and the transfer means for transferring the transferred object as described above encounters several disadvantages.
One of the disadvantages is that it is highly troublesome to accurately align the clean transfer carrier with each of the processing units when it is desired to combine the vacuum clean chamber with the unit.
Another disadvantage encountered with the proposed method is that once the combination between the clean transfer carrier and the processing unit is carried out, the clean transfer carrier is kept stationary, resulting in an operating rate of the clean transfer carrier being decreased. In particular, use of an unmanned carrier as the clean transfer carrier fails to permit it to be diverted to different purposes.
A further disadvantage of the proposed method is that incorporation of the transfer means such as a robot in the vacuum clean chamber of the clean transfer carrier causes a size of the vacuum clean chamber to be excessively increased, so that much time is required for evacuation of the vacuum clean chamber carried out after it is combined with each of the processing units and a period of time for which the vacuum cleans chamber is kept at a vacuum after it is released from the processing unit is substantially reduced.
The proposed method has still another disadvantage that a large-sized vacuum unit such as a vacuum stocker or the like is required for storage of the transferred object.